Process of refining hydrocarbon oils



July 30, 1940- J. w. wElR PROCESS 0F REFINING HYDROCARBON OILS Filed NOV. 22, 1938 lsf-E- @-5- fla-mas W-We1- @L7M ma.,

Kia' @WO1/MM35 Patented July 30, 1940 PATENT OFFICE 2,209,865 PROCESS OF REFIIvsG HYDROCARBON James Weir, Los Angeles, Calif., assigner, by mesne assignments, to Edeleanu Gesellschaft m. b. H., Berlin, Germany,

Germany a corporation of Application November 22, 1938, Serial No. 241,871

'4 Claims.

This invention relates to the treatment of hydrocarbon oils, containing normally liquid components of high viscosity index and low viscosity index along with wax.

More particularly, the invention is concerned with the separation of the low viscosity index hydrocarbons, generally defined as naphthenic constituents, from the normally liquid high viscosity index hydrocarbons, which are herein referred to as parainic constituents, and from the wax. This separation is effected by means of selective solvents wliich exert a preferential solvent action for the former group of components and substantially no solvent action upon the l normally liquid high viscosity index components and upon the solid wax. The invention further comprises separating the wax from the oil. This dewaxing step may be carried out on the unrelned waxy stock or the wax may be removed from the solvent refined oil, or waxy raffinate as it is called.

One of the objects of this invention is, as will be clear from the following description, to effect dewaxing of a mineral oil in a heterogeneous solvent-oil system; and another object is to separate the waxy oil-solvent mixture into two phases, from which the non-Wax-containing extract phase can be removed bydecantation without filtering.

A further object is to obtain a high yield of refined oil of good quality and low wax content without excessive chilling.

Other objects and advantages pertain to the specific solvent used, as hereinafter described.

Recent developments in the art of solvent reflning of lubricating oils, obtained from petroleum fractions, permit the manufacture of high grade lubricants from relatively low grade lubrieating oil stocks. For example, it has long been known that so-called asphaltic or naphthenebase crudes contain a substantial percentage of valuable paraffin-base constituents, particularly when such crudes contain noticeable quantities of parain wax. Such crudes are generally known as mixed base crudes. I

It is a rather ditiicult problem to remove the wax associated with the lubricating oil stock either preparatory to or after solvent refining.

Processes of accomplish wax removal have been made available to the industries at various intervals and such methods are too well known to those skilled in the art to require mention, but recent developments in dewaxing of lubricating oils have assumed industrial importance and appear outstanding enough to warrant further description for purposes of comparison with my invention. At the present three such methods are applied commercially on a large scale.

l. The propane dewaxing process,` using propane s as a self-refrigerant and wax precipitating agent at low temperatures. m

2. The benzol-acetone dewaxing process,l using external refrigeration and various benzolacetone ratios, depending upon the type of m lubricating oil stock treated.

3. The use of chorinated hydrocarbons `:uch as for instance tri-chlor-ethylene, chloroform or carbon-tetrachloride, usually externally refrigerated and cold centrifuged to accomplish sepu aration of the precipitated wax.

All of the above described processes depend` upon low temperature refrigeration to precipitate the wax, and none of the methods listed is capable of precipitating wax at room tempera- 20 tures to any appreciable extent, although benzolacetone will cause a small amount of Wax precipitation but not enough to be of any importance.

Furthermore a dewaxed oil of naphthene-base 25 characteristics does not represent a finished lubricant. The dewaxed oil must be solvent refined for the purpose of separating the naphthenic constituents from the paraiflnic fractions. It is absolutely essential to accomplish this separa- 30 tion if a high grade lubricant is desired since it is well known that improvements in viscosity index, gravity, resistance to oxidation and sludging are dependent upon high paraiiinicity. Naphthenes, while they make good lubricants when new, de- 35 teriorate rapidly during use in the crankcase. They are easily oxidized, polymerized and show therefore great tendencies to form sludge. The gravity of such naphthenes is very low due to the lower hydrogen content of the molecules. This 40 low hydrogen content is thought to be chiefly responsible for the instability of such constituents in lubricating oils.

Many solvents have been proposed to accomplish selective separation of naphthenic and par- 45 afflnic constituents and it is only necessary to mention the most widely used reagents. All such solvents dissolve more or less efiiciently the naphthenic constituents, leaving the more paraflinic fractions unaffected. A separation is accom- 50 plished while forming a two-phase system, the lower phase being known conventionally as the extract phase, and the upper phase being known as the railnate phase. The extract phase consists chiey of solvent containing a smaller l amount of naphthenic constituents, whereas the rainate phase contains but a small amount of solvent and consists principally of paraiiinic constituents, i. e., desired lubricating oil fractions of high quality. The treating temperature and the solvent-oil ratio are the controlling factors for efiicient operation during solvent refining and their practical limits and effects are too well known to those skilled in the art to need further comments.

AThe principal selective solvents used at the present on a large scale may be summarized as follows:

a. Propane and cresylic acid or propane and a mixture of phenol and cresylic acid (Duo-solprocess).

b.Phenol, both aqueous and anhydrous.

c. Chlorex, (di-chlor-di-ethyl ether).

d. Sulphur dioxide with or without benzol modification (Edeleanu process).

e. Furfural, and many others.

When comparing the previously listed dewaxing solvents with the above listed refining solvents it can be seen that none of the solvents listed is capable of accomplishing by itself both solvent refining and dewaxing. Propane, while used alone as a dewaxing-solvent, is not capable of acting as a selective solvent. Only when propane is used with the addition of other solvents is it of value, as for example in the duosol-process, in which it serves the purpose of improving the color of the finished oil and also the carbon residue. Propane by itself has absolutely no selectivity for oil constituents excepting asphalt, which it is capable of precipitating; but an oil suitable to solvent refining usually does not contain asphalt since this product is conventionally removed by vacuum distillation while preparing the lubricating oil stock from the crude petroleum.

It is an object of this invention to provide a suitable common solvent for both dewaxing and refining operations, which is both very efficient and so flexible as to be adapted to all types of crude oils. This dual purpose solvent invention enables many improvements to be introduced in the art of dewaxing and solvent refining, as will be described in detail.

The invention is illustrated by three diagrams (Figs. 1, 2 and 3) showing its application in various ways to the production of substantially oil-,free high melting parafiin wax and low pour point dewaxed lubricating oil of high quality from waxy lubricating oil stocks containing both high and low quality constituents. Figs. 2 and 3 are modifications of Fig. 1, Fig. 2 being substituted for the portion of the diagram to the right of broken line A and Fig. 3 being substituted for the portion of the diagram to the right of broken line B in Fig. 1, respectively.

It is well known that almost any liquid which is capable of dissolving the waxy oil can be used as a dewaxing reagent provided such a liquid does not solidify at the low temperatures to which the mixture must be cooled to precipitate the wax. Anhydrous pyridine as well as many other organic solvents is suitable to dewaxing of oils, but pyridine is superior to any of the conventionally used solvents in that it is capable of producing a low pour point oil at a much higher temperature. For example, propane-waxy lubricating oil mixtures must be chilled to about 45" F. to produce a 0 F. cold test oil; benzol-acetone waxy lubricating oil mixtures must be cooled to 15 F. to produce a 0 cold test oil, etc.

Pyridine without amr modifying agent is capable of producing a low pour point or cold test oil, the cold test of which is directly equivalent to the temperature to which the pyridine waxy lubricating oil mixture is chilled.

Since pyridine solidies at below 40 F. it is possible to obtain with this reagent extremely low cold test oils which for example the benzolacetone reagent could not easily produce on account of the high solidication point of the benzol. Also propane-waxy lubricating oil mixtures would have to be chilled to very low temperatures to produce as low a cold test oil as it is possible to obtain with pyridine.

Experience acquired by those skilled in the art of solvent dewaxing has shown that it is difiicult to prevent the wax cake from retaining large quantities of oil when filtering at low temperatures, for example a well known process produces a wax cake containing anywhere from 50 to oil. This oil is usually lost if no attempt is made to renne the filter wax, using methods which will permit the recovery of the oil absorbed by the wax crystals.

The amount of oil retained in the wax cake decreases with the increase of filtration temperature and pyridine without any modification is capable of producing a much drier wax cake resulting consequently in a higher yield of dewaxed oil than heretofore.

A remarkable improvement results when preparing a modified pyridine solvent for the purpose of dewaxing. I have found that when pyridine is modified with small quantites of water (H2O) or any other compound soluble in pyridine but insoluble in the oil phase, a dewaxing solvent is produced which is capable of precipitating practically all the wax contained in the oil at ordinary atmospheric temperatures (say from at 60 to 80 F.) which may be considered as .normal temperature for the purposes of this invention.. l

I prefer to use water as a modifying agent for room temperature dewaxing of oils for reason of economy. The amount of water modification of the pyridine depends upon the type of oil to be treated and also upon the wax content of the oil.

fornia lubricating oil distillate of the mixed base type containing about 13% wax, as follows:

So-called technical pyridine having an initial boiling point of 280 F. when in anhydrous filtration without any difliculty. It is not nec'-,k

essary to first permit the waxl to oat to the surface before commencing filtration. Preferably the waxy lubricating stock should be added at a somewhat elevated temperature followed by gradual cooling to room temperature, but very good results in precipitation and filtering were also obtained when adding the waxy material in a somewhat sticky consistency to the solvent. followed by thorough agitation.

I have discovered a very efficient dewaxing method for treatment of a waxy Cali- It is therefore one object of my invention to separate oil and wax from each other by means of a solvent of the class of pyridine. pyridine homologues and mixtures thereof after having been modified by the addition of water.

Another object of my invention is to permit the wax precipitate to float to an upper zone. drawing olf the lower oil-solvent phase and ltering such part of the mixture only as is composed of dispersed wax and oil. Depending upon the amount of water added to the pyridine as a modifying agent it is possible to form a two phase system of a. A lower extract phase containing napthenic constituents plus modified solvent.

b. An vupper phase (rafiinate phase) containing paraiiinc constituents through which the precipitated wax is dispersed.

The reason for such phase separation is due to the fact that this modified dewaxing solvent becomes also a selective refining solvent giving a two-phase separation. This phase separation depends primarily upon the extent of water modification and treating temperature but it can be avoided if desired by decreasing the water content of the modified solvent. e

I have observed that the extent of wax precipitation is, up to a certain limit, a function of the water modification. More water will result in a more extensive wax precipitation and it' is desirable to work with as large a water content as wpossible. On the particular stock treated as described above, a 4% water content gave very good results.

When a phase separation is produced, I have found it to be advantageous to draw off the lower extract phase before filtering the upper ramnate phase which contains the precipitated wax. This, however, is not essential and I shall not limit this invention to the specific example given above. Many deviations in the art of filtering or othern wise separating the precipitated wax may be made without deviating from the spirit of this invention.

If it is found desirable to draw ofi the lower extract phase before filtering it is assured that this mixture is essentially free from wax and requires no further dewaxing.

I have found that the particular waxy Callfornia lubricating oil stock in question showed a 55 F. coldtest when ltered at plus 70 F. The original cold test of the waxy lubricating oil stock was F. The wax-cake was washed with about one-half volume of modified solvent leaving a white, high melting point wax as a residue, free of oil.

Since this particular oil as well as any other waxy lubricating oil stock shows at first a very rapid increase in pour point with small increase in wax content the astounding fact was established that at least 98% of the total wax content was removed with this modified solvent at plus 70 F. A 55 F. pour point is equivalent to from 1 to 2% wax content. This was determined by careful studies of the wax-oil relationship upon the stock in question.

The filtrate consisting of almost completely dewaxed oil had separated into a. two phase extract and raiiinate system. The extract phase was drawn off and the rainate phase was freed of solvent by distillation. The finished raffinate showed a. 25.5 A. P. I. gravity. The gravity of the waxy lubricating oil stock was about 22 10W pour dewaxed oil since no solvent refining is accom-v plished with any of the dewaxing solvents dur-= ing dewaxing operations.

It will, therefore, be seen that I have suc-s ceeded during the course of experiments in de waxing said lubricating oil stock at plus '70 F. and simultaneously improving the viscosity index and raise the gravity of the oil from 19.5 to 25.5 A. P. I., an increase of 8 volumes of modified solvent. v

I have further succeeded in producing from the same lubricating oil stock a still lower pour point oil, namely +40 F.. 'when ltering at plus 70 F. and when using the same solvent in a some= what larger volume and containing a somewhat larger volume of water. Essentially, the dewaxing procedure best suited to emcient consists of two steps: About 2 volumes of modified solvent are mixed with one volume of waxy lubricating oil stock and agitated at `room tem perature until the precipitated wax appears to be well leached. This is indicated bythe yellow appearance of the wax precipitate. The t`ure may now be filtered without permitting any phase separation winch would take place were the mixture allowed to remain at rest; or if so desired the material may be kept at rest to per mit the precipitated wax to oat into the upper raiiinate phase and then separated into extract and ramnate phases before nltering the latter, as illustrated in Fig. 1. If settling time is allowed before filtering, it is best to draw oir the extract phase and iilter the ramnate phase only.

This filtered rainate may be rened to a. xra ished high gravity oil by further selective solvent refining, or it may firstbe chilled to a moderately low temperature and ltered to remove the ai 1 or 2% of wax for the purpose of producing a point oil, as illustrated in Fig. 3. Ii dewaxing operation is carried out immediately following the room temperature dewaxing it is advisable to add a small amount of anhydrous pyridine-solvent, previous to chilling the raflnate. The chilled rainate-solvent-mixture is again filtered and a low cold test oil will result. The cold test ci the finished oil depends upon the temperature at which the mixture is ltered. .A 0 F. ltration temperature will give a 0 F. pour point oil. l

It may be advisable to further solvent ree the ranate, which has been partially dewaxed at room temperature, before performing the above operation the inal A. P. using 2]/2 outlined nai dewaxing operation, as illustrated in Fig. 3.

Yield determinations during dewaxing Yoperations were conducted by combining both the extract phase and the rainate phase resulting from the dewaxing operation, topping o of the total solvent and determining the volume oi the total oil recovered.

It was found that the lubricating oil stock which contained about 11 volume percent of wax yielded from 86 to 88% dewaxed oil without any filter aid. This value is about the maximum that can be expected from any dewaxing process and exceeds by far the eiliciency of any of the commercially applied modern processes.

The over-al1 yield of rened and dewaxed oil of 29.0 A. P. I. gravity, based on charging stock, as obtained in accordance with my process, is much higher than the usual yields obtained when dewaxing this same material with propane or benzoi acetone, followed by Soz-benzol, phenol nr propane-cresyiic acid extraction.

What I claim is:

1. A process of extracting and dewaxing a hydrocarbon oil containing normally liquid parafflnic and naphthenic constituents'and wax, comprising mixing said oil with a solvent of the class consisting of pyridine, pyridine homologues and mixtures thereof, said solvent containing a sumcient amount of Water to produce a separation into two phases at normal temperature, namely a rafllnate phase comprising the normally liquid parailinic constituents and substantially all of the wax, both containing some solvent dissolved therein, and an extract phase comprising the naphthenic constituents and substantially all of the water, both being dissolved in said solvent,

adjusting the temperature of the mixture to about 70 Fahrenheit, separating the extract phase from the raiiinate phase, filtering the raiiinate phase at about 70 Fahrenheit to separate the solid wax therefrom and to produce a partially dewaxed oil having a pour point of from to 25 degrees Fahrenheit below .the temperature of iiltration, and recovering the solvent from the extract phase, the partially dewaxed ranate phase and from the wax.

2. A process of extracting and dewaxing a hydrocarbon oil containing normally liquid parafiinic and naphthenic constituents and wax, comprising mixing said oil with a solvent of the class consisting of pyridine, pyridine homologues and mixtures thereof, said solvent containing a sufficient amount of water to produce a separation into two phases at normal temperature, namely a ranate phase comprising the normally liquid paraiiinic constituents and substantialiy all of the wax, both containing some solvent dissolved therein, and an extract phase comprising the naphthenic constituents and substantially all of the water, both being dissolved in said solvent, separating the extract phase from the raiiinate phase, ltering the rainate phase at a temperature substantially above 50 Fahrenheit to separate the solid wax therefrom, and to obtain a rst wax-cake and a first iiltrate, diluting said first flltrate with an additional amount of an anhydrous solvent of the class of pyridine, pyridine homologues and mixtures thereof, chilling said diluted iirst iiltrate to a low temperature,-

whereby the remaining wax separates out as a solid phase, in mixture with the chilled diluted irst filtrate, iiltering said last mentioned mixture at a low temperature to obtain a second wax-cake and a second filtrate, said second filtrate comprising the completely dewaxed raiiinate dissolved in the anhydrous solvent, and recovering the solvents from the extract solution, the completely dewaxed rainate solution, the first wax-cake and from the second wax cake.

3. A process of extracting and dewaxing a hydrocarbon oil containing normally liquid parafiinlc and naphthenic constituents and Wax, comprising mixing said oil with a solvent of the class consisting of pyridine, pyridine homologues and mixtures thereof, said solvent containing a sufficient amount of water to produce a separation into two phases at normal temperature, namely a raiiinate phase comprising the normally liquid paraflinic constituents and substantially all of the wax, both containing some solvent dissolved therein, and an extract phase comprising the naphthenic constituents and substantially all of the water, both being dissolved in said solvent, adjusting the temperature of the mixture to about 70 Fahrenheit, ltering said mixture at about '70 Fahrenheit to obtain a wax-cake and a iiltrate comprising a two-phase system namely, said extract phase and a partially dewaxed railinate phase, separating said last mentioned phases from each other, to produce a partially dewaxed oil having a pour point of from 15 to 25 Fahrenheit below the temperature of filtration.

4. A process of extracting and dewaxing a hydrocarbon oil containing normally liquid paraffinic and naphthenic constituents and wax, comprising mixing said oil with a solvent of the class consisting of pyridine, pyridine homologues and mixtures thereof, said solvent containing a sufficient amount of water to produce a separation into two phases at normal temperature, namely a raffinate phase comprising the normally liquid paraiinic constituents and substantially all of the wax, boi containing some solvent dissolved therein, and an extract phase comprising the naphthenic constituents and substantially all of the water, both being dissolved in said solvent, ltering said mixture at a temperature substantially above 50 Fahrenheit to separate the solid wax therefrom and to obtain a first wax-cake and a rst ltrate, said iirst filtrate comprising a two-phase system, namely said extract phase and a partially dewaxed rainate phase, separating the phases of said first filtrate from each other, diluting said partially dewaxed Iainate phasewith an additional amount of an anhydrous solvent of the class of pyridine, pyridine homologues and mixtures thereof, chilling said diluted partially dewaxed raffinate phase to a low temperature, whereby the remaining wax separates out as a solid phase in mixture with the chilled diluted partially dewaxed rainate phase, ltering said last mentioned mixture at a low temperature to obtain a second wax-cake and a second filtrate, said second filtrate comprising the completely dewaxed raffinate dissolved in the anhydrous solvent.

JAMES W. WEIR. 

